Sir Alex announced his retirement as manager of Manchester United after 27 years in the role. He has gone out in a blaze of glory, with United winning the Premier League for the 13th time, and he is widely considered to be the greatest manager in the history of British football.Over the last quarter of a century there have been seismic changes at Manchester United. The only constant element has been the quality of the manager's league-winning squad and United's run of success, which included winning...